The proposed research is aimed at determining the molecular basis of amoeboid movements. The research will integrate information from three levels of organization (1) whole cells, (2) cell models of structure and motility and (3) the interactions of purified proteins. The specific objectives of the proposed research are: (a) to identify, characterize and reconstitute the calcium and pH sensitive components of the contractile-cytoskeleton from amoeboid cells, (b) to characterize the assembly of actin in vitro and in vivo using microspectrofluorometric techniques, (c) to identify the distribution and dynamics of actin in vitro and in vivo, (d) to map intracellular pH and Ca ions using ratio photometry and aequorin luminescence, (e) to characterize the structure and kinetics of gelation in vitro and in vivo using fluorescence photobleaching recovery.